Air hammer optimization using acoustic telemetry

ABSTRACT

A system and method of optimizing air hammer performance in a well drilling rig whereby an electronic acoustic receiver (EAR) is used to monitor the effects of changing any of the operating parameters under his or her control. The signals are visually presented to the drill operator based on an EAR&#39;s output, along with current settings, allowing the drill operator to dial in the parameters of his or her choice until the optimal frequency of the air hammer is regained. The visual output displays the amplitude response of acoustic waves being detected and decoded at the surface by the EAR. The drill operator can observe and use this information to determine the changes necessary in the operating parameters to return the hammer to optimal frequency, and thus optimal performance.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority in U.S. patentapplication Ser. No. 12/815,074, filed Jun. 14, 2010, which claimspriority in U.S. Provisional Patent Application No. 61/187,200, filedJun. 15, 2009, both of which are incorporated herein by reference. Thisapplication relates to U.S. patent application Ser. No. 12/697,938,filed Feb. 1, 2010, which is also incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to telemetry apparatus andmethods, and more particularly to a method utilizing telemetry data forthe optimization of the performance of air hammer type drilling systemsfor the well drilling and production (e.g., oil and gas) industry.

2. Description of the Related Art

Acoustic telemetry is a method of communication used, for example, inthe well drilling and production industry. In a typical drillingenvironment, acoustic extensional carrier waves from an acoustictelemetry device are modulated in order to carry information via thedrillpipe as the transmission medium to the surface. Upon arrival at thesurface, the waves are detected, decoded and displayed in order thatdrillers, geologists and others helping steer or control the well areprovided with drilling and formation data.

It is well known that acoustic extensional waves can propagate throughdrill pipe if they contain frequencies that correspond with thepassbands formed by the regular mechanical dimensions of drill pipe. Useof this communications channel enables real-time drilling telemetry tobe the means by which drilling parameters (such as directional andformation) measured relatively close to the drill bit are sent to thesurface. At the surface, the signals can be detected by a sensitiveaccelerometer whereby, after filtering and amplifying the signal, wellinformation may be made available to the driller. An example of such asystem is an Electronic Acoustic Receiver (EAR), which is detection andamplifying means to connect to a processor module and an RF system,thereby enabling two-way communication between the driller and the EAR.

Many practical mechanical means are utilized when drilling for oil andgas. A modern and popular approach is to ‘hammer’ at rock formationsrather than using traditional rotary drills, which are limited to movingforward. Hammer drilling requires that the drilling fluid be a gasrather than a liquid, whereas rotary drilling requires the drillingfluid to be a liquid. Traditional rotary drill liquid motors used torotate the drill bit are replaced by an air hammer in modern hammerdrilling machines. This air hammer pounds the rock into small pieces bya rapid axial reciprocating motion.

Air hammers require a number of parameters to be in balance in order toachieve efficient forward progress. The main issues are to balance theair flow to the hammer with an appropriate weight on the hammer bit. Ifthere is too much weight on the bit the hammer stroke is reduced,resulting in reduced penetration of the rock. Similarly, if there is toolittle weight on the bit then the work done by the hammer is reduced,again resulting in reduced rock penetration. If the air flow poweringthe hammer is too small, rock fragments may not clear the device and mayjam the mechanism, whereas too much airflow can result in hammer bitdamage. A balance of these parameters results in an ideal frequency andoptimized rate of rock penetration.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to immediately provide feedbackto drill operators utilizing air hammer drill systems. This inventionprovides the driller a direct visual indication of this event, andimmediately shows effects due to changing any of the parameters underhis or her control (e.g., air flow and hammer weight).

The signals are provided to the driller by the EAR's output beingvisually presented to the driller, along with current settings. Thisallows the driller to dial in the parameters of his or her choice untilthe optimal frequency is regained.

The visual output on screen displays the amplitude response of acousticwaves being detected and decoded at the surface by the EAR. It is thenpossible to process these amplitudes so that they show the Fouriertransform of the amplitude response.

The advantage to such a system is that the transform shows the frequencyresponse in real time of the air hammer working. As the hammer changesthe rate at which it strikes the rock, the frequency display willfaithfully follow by means of the acoustic channel from the hammer tothe EAR at the surface.

It is this information that the drill operator can observe and use todetermine the changes necessary in the system parameters to return thehammer to optimal frequency, and thus optimal performance. Anydeviations from this necessitated by changing rock conditions can beaccommodated by surface control, and the effect of these changes becomeimmediately apparent, thereby enabling to just timely feedback to thedriller but also the means to automate the changes necessary for optimalperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate the principles of thepresent invention and an exemplary embodiment thereof:

FIG. 1 is a diagram of the normal passbands of Range 2 drilling pipe;and

FIG. 2 is an example of an EAR's output being visually presented on acomputer screen.

FIG. 3 is a diagram of a typical drilling rig, including an air hammeroptimization system embodying an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, reference is made to “up” and “down”waves, but this is merely for convenience and clarity. It is to beunderstood that the present invention is not to be limited in thismanner to conceptually simple applications in acoustic communicationfrom the downhole end of the drillstring to the surface. It will bereadily apparent to one skilled in the art that the present inventionapplies equally, for example, of subsurface stations, such as would befound in telemetry repeaters.

Referring to the drawings in more detail, FIG. 1 displays the normalpassbands of Range 2 pipe. This is one example of what information maybe provided during drilling operations, and the present invention is inno way limited to only Range 2 pipe.

FIG. 2 shows an example of a visual display a drill operator may seewhile operating the air hammer drill with the present invention. Thedisplay would appear on a computer screen, accessible by the driller,and directly connected to the air hammer drill system as well as theEAR. Results displayed on the screen are to be in real time, with theamplitude response of acoustic waves being detected and decoded at thesurface displayed on the screen. Other information relevant to theoperation of the air hammer drill system is individually selectable andviewable on screen.

The reference numeral 2 generally designates an air hammer optimizationsystem. Without limitation on the generality of useful applications ofthe system 2, an exemplary application is in a drilling rig 4 as shownin a very simplified form in FIG. 3. For example, the rig 4 can includea derrick 6 suspending an air hammer actuator 8, which receives gas viaa compressor hose 20 for pumping downhole into a drillstring 22. Thedrillstring 22 and the air hammer actuator 8 are connected to the system2 which includes an EAR/detector 16, an amplifier 14, a filter 12, and acontroller 10. The drillstring 22 connects to multiple drill pipesections 24, which are interconnected by tool joints 18, thus forming adrillstring of considerable length, e.g. several kilometers, which canbe guided downwardly and/or laterally using well-known techniques. Thedrillstring 22 terminates at an air hammer apparatus 32. In FIG. 3 wehave shown acoustic modules (isolator 30 and transmitter 28) as separatefrom the conventional air hammer simply for clarity. Other rigconfigurations can likewise employ the air hammer optimization system ofthe present invention, including top-drive, coiled tubing, etc. Thecontroller 10 includes a manually selectable input 34 for selecting anumber of parameters undergone by the drill during operation. Theseparameters generally include bit weight, air flow, and hammer rate.

Information such as that contained in FIG. 1 will pass up a drillstringor up the drill pipe and be read by an EAR. This information will thenbe decoded, and relevant information will be displayed on screen.Relevant information includes, but is not limited to, bit weight, airflow, hammer rate, and relevant frequencies. This information can beused by the drill operator or by a system designed to automaticallyreturn the drill operation to optimal rock penetration by recalibratingbit weight, air flow, and other parameters.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:
 1. A system for optimizing airhammer performance in a well drilling rig including a drillstring, whichcomprises: an air compressor connected to the drillstring; a bitconnected to the drillstring; a controller connected to the compressorand the drillstring; an air hammer attached to a downhole end of thedrillstring, said air hammer having performance parameters including apercussive rate corresponding to an air flow from said compressor andbit weight, a penetration rate, and a frequency response; an acoustictelemetry subsystem associated with the air hammer and adapted fortransmitting said frequency response via acoustic waves along thedrillstring; said controller adapted for operating said actuator; saidcontroller including a manually selectable input for selectingparameters selected from the list comprising bit weight, air flow, andhammer rate; a feedback input, the feedback input being responsive tosaid frequency response; said controller programmed to automaticallyadjust for optimal settings an operating parameter of said air hammer inresponse to said frequency response, said operating parameters includingair flow from said compressor and said bit weight; and said controllerbeing adapted to adjust said bit weight on said air hammer, said bitweight comprising an operating parameter of said air hammer.
 2. Thesystem according to claim 1, further comprising: an electronic acousticreceiver (EAR) connected to the drillstring and the controller, said EARbeing adapted for receiving acoustic waves therefrom and detecting theair hammer frequency response.
 3. The system according to claim 1,further comprising: a display device connected to said controller andadapted for displaying a real-time graphic display of the frequencyresponse of said air hammer.
 4. The system according to claim 1, furthercomprising: said controller being adapted to adjust said air flow tosaid air hammer, said air flow comprising an operating parameter of saidair hammer.
 5. A system for optimizing air hammer performance in a welldrilling rig including a drillstring, which comprises: an air compressorconnected to the drillstring; a bit connected to the drillstring; acontroller connected to the compressor and the drillstring; an airhammer attached to a downhole end of the drillstring, said air hammerhaving performance parameters including a percussive rate correspondingto an air flow from said compressor and bit weight, a penetration rate,and a frequency response; an acoustic telemetry subsystem associatedwith the air hammer and adapted for transmitting said frequency responsevia acoustic waves along the drillstring; said controller programmed toautomatically adjust for optimal settings an operating parameter of saidair hammer in response to said frequency response, said operatingparameters including air flow from said compressor and said bit weight;an electronic acoustic receiver (EAR) connected to the drillstring andthe controller, said EAR being adapted for receiving acoustic wavestherefrom and detecting the air hammer frequency response; a displaydevice connected to said controller and adapted for displaying areal-time graphic display of the frequency response of said air hammer;said controller adapted to adjust said air flow to said air hammer, saidair flow comprising an operating parameter of said air hammer; saidcontroller adapted to adjust said bit weight on said air hammer, saidbit weight comprising an operating parameter of said air hammer; anactuator, connected to said compressor; said controller adapted foroperating said actuator; said controller including a manually selectableinput for selecting parameters selected from the list comprising bitweight, air flow, and hammer rate; and a feedback input, the feedbackinput being responsive to said frequency response.
 6. The systemaccording to claim 5, which includes an acoustic isolator for use withtubular assemblies including an acoustic wave transmitter, whichacoustic isolator comprises: a first coaxial tubular member with a firstmember length including a proximal end and a distal end, a firstacoustic impedance and a first acoustic transit time; a second coaxialtubular member with a second member length including a proximal end anda distal end, a second acoustic impedance and a second acoustic transittime; the first and second tubular members being aligned so as not to bein physical contact; a first coupling located at the proximal end of thefirst and second members, said first coupling restricting the motions ofsaid members and said coupling whereby said motions are approximatelyequalized at their common points of contact thereby allowing exchange ofacoustic energy between the tubular assemblies above said first couplingand said tubular members below said first coupling; a second couplingplaced at the distal end of the first and second members, said secondcoupling restricting the motions of said members to be equal at theircommon points of contact thereby allowing exchange of acoustic energybetween the tubular assemblies below said second coupling and saidtubular members above said second coupling; the lengths, acousticimpedances, and transit times of said tubular members aligned so that bymeans of constructive and destructive wave interference the acousticenergy transmitted through the upper coupling results in reduced motionand reduced force in the second coupling, and acoustic energytransmitted through the lower coupling results in reduced motion andforce in the first coupling whereby downward traveling acoustic energyis selectively reflected upward and upward traveling acoustic energy isselectively reflected downward; the first and second coaxial tubularmembers comprised of dissimilar materials, such that acoustic wavesoriginating at the distal end travelling along said coaxial tubularmembers travel at substantially different wave speeds; said dissimilarmaterials of equal impedance value; and said differing wave speedsinducing a phase difference between said coaxial tubular members, saidphase difference depending on the length of the members.
 7. A method ofoptimizing air hammer performance in a drilling rig including a wellheadand a drillstring, which method includes the steps of: providing acompressor at the wellhead; providing an air hammer; providing a bitconnected to said drillstring; mounting said air hammer on a downholeend of said drillstring; pumping compressed air from said compressor tosaid air hammer via said drillstring; producing a frequency responsewith said air hammer in operation; transmitting said frequency responsewith acoustic telemetry to the wellhead via said drillstring; providinga controller at said wellhead; connecting the controller to thecompressor; programming said controller to automatically adjust foroptimal settings an operating parameter of said air hammer in responseto said frequency response, said operating parameters including air flowfrom said compressor and said bit weight; providing a feedback signalfrom said air hammer via said drillstring to said controller; providingan electronic acoustic receiver (EAR) at the wellhead; connecting theEAR to the drillstring and the controller; detecting with the EAR an airhammer frequency response in the form of acoustic waves; displaying asvisual output on said display device an amplitude response of saidacoustic waves being detected and decoded; processing said amplitude toshow a Fourier transform of said amplitude response; selecting otherinformation relevant to the operation of the air hammer drill system onsaid display device; and adjusting the operating parameters with saidcontroller for optimizing performance of said air hammer, said operatingparameters including air flow from said compressor and said bit weight.8. The method according to claim 7, which includes the additional stepsof: providing a first coaxial tubular member of a first length andincluding a first diameter, a proximal end and a distal end; providing asecond coaxial tubular member of a second length and including a seconddiameter, a proximal end and a distal end; placing said first tubularmember inside said second tubular member, wherein the members are not inphysical contact, forming an acoustic isolator; providing a pair ofcouplers located at the proximal and distal ends of said members, thecouplers being adapted for connection to other like collars attached tosaid drillstring assembly sections; generating acoustic transmittersignals with the BHA; transmitting acoustic wave signals from the BHAupwardly through said drillstring assembly sections; and acousticallyfiltering said signals with said acoustic isolator by either or both ofthese steps of filtering or reflecting said acoustic wave signals alongsaid drillstring.